Gary F Massart
Bile Acids (BAs) constitute an important class of biological molecules produced in the metabolism of all vertebrates. In mammals, they exhibit the so called C24 structure: 24 carbon atoms form a steroid nucleus (three six-member rings indicated as A, B C and a five-member ring indicated as D) and a fivecarbon side chain with a carboxyl group at the C-24 position. The A and B rings are linked in cis configuration, inducing an overall bent shape. Such a structural feature delineates a concave and convex side of the steroidal backbone where OH groups in α orientation (up to three) and two methyl groups in β orientation, respectively, point out. Therefore, two opposite faces with hydrophilic and hydrophobic properties can be distinguished. Further variations of the molecular structure can be observed at C-3 carbon due to hydroxyl, sulfate or glucuronate substituents. C-6 and C-24 glucoronide conjugates were also found in humans. Other C-24 substituents are glycine or taurine.
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